Syntheses for (4-nitrosophenyl)phenylhydroxylamine, which have been previously described, have started only from nitrosobenzene. Nitrosobenzene is dimerized in strongly acid medium to give (4-nitrosophenyl)phenylhydroxylamine when the following acids are used, such as sulfuric acid (Bamberger et al., Chem. Ber., 31 (1898), 1513; DE 2020043), peroxytrifluoroacetic acid (Boyer, J. Org. Chem. 24 (1959) 2038), hydrofluoric acid (Wiechert, Z. Chem. 15 (1955) 21; DE 1147237), sulfonic acids, perchloric acid, trifluoroacetic acid (DE 2703919) and Lewis acids such as, for example, BF.sub.3 xOEt.sub.2 (EP 9267).
(4-nitrosophenyl)phenylhydroxylamine is also formed as a secondary product when reacting nitrosobenzene with alcoholates as bases, (Aurich et al., Liebigs Ann. Chem. (1981), 1271-1281; Hutton, Waters, J. Chem. Soc. (B) (1968) 191).
A serious disadvantage of the processes described is that they use nitrosobenzene as a starting material and this cannot be prepared in an economically viable manner, in particular, from inexpensive nitrobenzene, on an industrial scale (Kochetova, Klyuyev, Petroleum Chemistry, vol. 37, (1997), 414-421).
It was, therefore, desirable to develop a process for preparing (4-nitrosophenyl)phenylhydroxylamine which uses a more cost-effective and less expensive starting material than nitrosobenzene.